A MIMO (Multiple-Input Multiple-Output) system realizes high quality and high-speed transmission by effectively using a limited frequency band and is recently focused. The MIMO system simultaneously transmits/receives independent signals in the same band through a plurality of eigen vectors using a plurality of antennas for both transmission and reception. Compared with a single antenna system, the MIMO system can expand the transmission communication capacity without expanding the frequency band by using a plurality of antennas so that it is possible to improve the transmission rate.
A technology introducing STTD (Space-Time Transmit Diversity) to a system applying MIMO is proposed so that it is possible to further improve the transmission rate of a radio communication system applying a MIMO technology. STTD is a technique for obtaining not only a temporal diversity gain but also a spatial diversity gain using two antennas by encoding between symbols transmitted through the corresponding antennas. The proposed technology incorporates the STTD technology into a system using four transmit antennas and has a configuration called a “DSTTD (Double-STTD) configuration.”
A DSTTD-SGRC (DSTTD-Sub-Group Rate Control) which introduces AMC into DSTTD is proposed so that it is possible to further improve the throughput of the system adopting the above DSTTD configuration. The AMC technology changes a modulation scheme or a channel coding rate adaptively and quickly. For example, it is possible to improve the transmission rate and improve the throughput of the system by using a faster modulation scheme and increasing a channel coding rate in a better propagation environment.
At present, DSTTD and DSTTD-SGRC technologies are already 3GPP (3rd Generation Partner Project) standards and are highly likely to be adopted for systems applying MIMO in the future. That is, it is possible to realize adaptive time-space diversity by simultaneously applying the STTD technology and AMC technology to a MIMO system.